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REACTIONS (CONTINUED..) Single Displacement Reactions
By the end of this lesson you will be able to: Demonstrate an understanding of the activity series for metals and halogens Predict products of a single displacement reaction
Single Displacement Reactions -One element in a compound is displaced (or replaced) by another element. Two types exist 1) A metal replacing a metal cation in a compound. (2 metals switching spots) 2) A non-metal (halogen) replacing an anion in a compound. (2 non-metals switching spots)
Example of Type 1: A metal replacing a cation (metal) Predict the products of the single displacement reaction below: Mg (s) + HCl (aq) MgCl 2(aq) + H 2(g) Rules: Treat hydrogen as a metal Treat acids as ionic compounds (HCl = H + Cl - ) Treat Water as ionic (H 2 O = H + OH - )
Example of Type 1: A metal replacing a cation (metal) Predict the products of the single displacement reaction below: Na (s) + H 2 O (l) NaOH (aq) + H 2(g) Rules: Treat hydrogen as a metal Treat acids as ionic compounds (HCl = H + Cl - ) Treat Water as ionic (H 2 O = H + OH - ) http://www.youtube.com/watch?v=eCk0lYB_8c0 http://www.youtube.com/watch?v=hqbwPxZsgHs&NR=1
Example of Type 2: A non-metal replacing a anion. Predict the products of the single displacement reaction below: F 2(g) + NaCl (aq) NaF (aq) + Cl 2(g)
Activity Series and Single Displacement Reactions Example: If we have the following reactions, which one will take place? Fe(s) + CuSO 4 (aq) → Cu(s) + FeSO 4 (aq) or Cu(s) + FeSO 4 (aq) → Fe(s) + CuSO 4 (aq) Will the reaction: Li + H 2 O LiOH(s) + H 2(g) The activity series is used to determine if a single displacement reaction will occur. (ref. pg.
We have looked at several reactions: Fe + CuSO 4 Cu + Fe 2 (SO 4 ) 3 Li + H 2 O LiOH + H 2 Such experiments reveal trends. The activity series ranks the relative reactivity of metals. It allows us to predict if certain chemicals will undergo single displacement reactions when mixed: metals near the top are most reactive and will displacing metals near the bottom. Q: Which of these will react? Fe+ CuSO 4 Ni+ NaCl Li+ ZnCO 3 Al+ CuCl 2 Cu + Fe 2 (SO 4 ) 3 Yes, Fe is above Cu NR (no reaction) No, Ni is below Na Zn + Li 2 CO 3 Cu + AlCl 3 Yes, Al is above Cu K Na Li Ca Mg Al Zn Fe Ni Sn Pb H Cu Hg Ag Au Yes, Li is above Zn
H is the only nonmetal listed. H 2 may be displaced from acids or can be given off when a metal reacts with H 2 O (producing H 2 + metal hydroxide). The reaction with H 2 O depends on metal reactivity & water temp. Q: will Mg react with H 2 O? K Na Li Ca Mg Al Zn Fe Ni Sn Pb H Cu Hg Ag Au cold H 2 O hot H 2 O steam acid NR A: No for cold, yes if it is hot/steam Mg + H 2 O H 2 + ZnCl 2 Complete these reactions: Al + H 2 O(steam) Cu + H 2 O Ca+ H 2 SO 4 Na+H 2 O H 2 + Mg(OH) 2 H 2 + Al(OH) 3 H 2 + CaSO 4 H 2 + NaOH Q: Zn + HCl
The more reactive metals are at the top of the activity series. The less reactive metals are at the bottom. A reactive metal will displace or replace any metal in a compound that is below in the activity series. So, sometimes, reactions will NOT occur!
All metals will have a specific place in the activity series. For simplicity, only the most common metals are shown. The metals near the top of the activity series are more reactive because their valence electrons are more easily removed. On tests and exams the activity series may appear as K, Na, … Ag, Au; you must remember that K is reactive, Au is not. If the valence of a metal is not indicated in the question, use its most common valence (in bold on your periodic table) to determine the correct chemical formula. Other Activity Series Information
Activity Series for halogens A reactive halogen will displace or replace any halogen in a compound that is below in the activity series. So, sometimes, reactions will NOT occur! This activity series mirrors the position of the halogens in the periodic table. Reactivity decreasesReactivity Increases F > Cl > Br > I Activity Series of Halogens
Using the Activity Series Note: If there is no reaction, write NR. Examples: 1) Cu(s) + MgSO 4 (aq) → 2) Zn(s) + FeCl 2 (aq) → 3) K(s) + H 2 O(l) → 4) Cl 2 + 2NaI → 5) I 2 + LiCl → Steps: Identify if the reaction will involve metals or halogens. Select the appropriate reactivity series (metal or halogen) Perform the switch If there is no reaction, write NR.